Adaptive Control for State Synchronization of Nonlinear Haptic Telerobotic Systems with Asymmetric Varying Time Delays

In this paper, we introduce a new adaptive controller design scheme for nonlinear telerobotic systems with varying time delays where the delays and their variation rates are unknown. The designed controller has the ability to synchronize the state behaviors of the local and the remote robots. In this paper, asymptotic stability in the presence of varying time delays is of interest. Using the proposed controller, asymptotic stability of the bilateral telerobotic system subject to any bounded yet unknown varying delay with a bounded yet unknown rate of change can be guaranteed. Besides the varying time delay, the proposed adaptive controller has the ability to adapt to the parameter variations in the local and the remote robots’ dynamics. It is shown that position and velocity errors between the local and the remote manipulators converge to the zero asymptotically, thus ensuring teleoperation transparency. Experimental and simulation results with a pair of PHANToM haptic devices and a pair of planar manipulators under varying time delays in the communication channel demonstrate the effectiveness of the proposed scheme.     

Non-parametric estimate of the system function of a time-varying system

The task of identifying an unknown dynamic system is made easier with prior knowledge on its behaviour. Using a frequency domain approach, the non-parametric maximum likelihood estimator of the system function, associated with the time-dependent impulse response of a time-varying system, is constructed. This is accomplished by the use of a simple linear least squares fitting algorithm, applied to the spectral response of the system to a multisine excitation. The noise variance on the system function is estimated simultaneously, and modelling errors can be detected, as illustrated on a simulation example.     

Integrating IPsec within OpenFlow Architecture for Secure Group Communication

Network securityprotocolssuch as IPsechave been used for many years to ensure robust end-to-end communication and are impor-tant in the context of SDN.Despite the widespread installation of IPsec to date,per-packet protection offered by the protocol isnot very compatible with OpenFlow and flow-like behavior.OpenFlow architecture cannot aggregate IPsec-ESP flows in transportmode or tunnel mode because layer-3 information is encrypted and therefore unreadable.In this paper,we propose using the Secu-rity Parameter Index(SPI)of IPsec within the OpenFlow architecture to identify and direct IPsec flows.Thisenables IPsec to con-form to the packet-based behavior of OpenFlow architecture.In addition,by distinguishing between IPsec flows,the architectureis particularly suited to secure group communication.     

Efflorescence control in geopolymer binders based on natural pozzolan

This paper addresses methods to reduce efflorescence in a geopolymer binder based on a pumice-type natural pozzolanic material from Taftan, Iran. Geopolymer pastes samples are analyzed for compressive strength and efflorescence formation after curing at 95% humidity for 28 days. To reduce the extent of efflorescence, Al-rich mineral admixtures such as metakaolin, ground granulated blast-furnace slag, and three types of calcium aluminate cements are incorporated into the dry binder at a range of concentrations. Hydrothermal curing at elevated temperatures also shows a positive effect in efflorescence reduction. Calcium aluminate cements show the greatest effect in efflorescence reduction, which is attributed to their dissolution in alkaline media releasing high amounts of alumina into the aluminosilicate geopolymer gel. These results confirm that it is possible to develop a more reliable geopolymer binder with improved properties either by adding a suitable amount of active alumina to precursors such as natural pozzolan, or by manipulating the curing conditions to enhance alumina release from less-reactive precursor phases.     

Modeling and Optimization of SE and SI of Copper Flotation via Hybrid GA–ANN

In the present paper, a new attitude has been proposed for optimization of the separation efficiency (SE) and the Gaudin’s selectivity index (SI) in a flotation process by Hybrid artificial neural network (ANN) and genetic algorithm (GA). The chemical reagent’s dosage (collector, frother and fuel oil), pH, solid percentage, feed rate, Cu, Mo, and Fe grades in the flotation feed were selected as input variables and the SE-Cu and SI-Mo and SI-Fe were selected as output ones. Multilayer NN with back propagation (BP) algorithm was trained by the standard Bayesian regulation algorithm in which the validation data set did not required to be apart from its training. This algorithm with four-layer was used to relate output and input variables. Employment of Hybrid GA–ANN method resulted in significant improvement on GA fitnesses, as SE-Cu = 88, SI-Mo = 4.47 and SI of Fe = 12.85 were achieved. The input parameters corresponding to the fitnesses were as follows: pH = 12.25; the grade of Cu = 0.55%, Mo = 0.04% and Fe = 5.53%; the collector, frother and fuel–oil concentrations being 16.55, 15.54 and 2.71 (g/ton), respectively; the solid percentage was 25.84% and feed rate was 38,380 ton/day. The best fitness of GA was obtained after 10 generations by MSE value of 2.23.     

A discrete model for simulating shear strength and deformation behaviour of rockfill material, considering the particle breakage phenomenon

This study focuses on numerical modelling of rockfill material with the discrete element method (DEM). This method was used due to the special features of rockfill material, such as intense particle breakage and high contracting behaviour, which are inherently due to large particle size. Because the DEM models the interaction of separate elements, it is capable of modelling discrete structures of granular materials and particle breakage. The model used in this study uses PFC^2D and considers breakable clumps. To validate the presented model for rockfill material, numerical single crushing tests and triaxial tests on the Purulia dam’s material were simulated. Due to the size-dependant crushing strength being involved in the breakage criterion, and also considering particle confinement, size-dependant and stress level-dependant behaviour was successfully simulated on modelled rockfill material. The variation of the sample’s particle grading from before the biaxial tests and after shear failure occurred was reported. The obtained results demonstrate the accuracy of the adopted model and the model’s capability for considering a rockfill material’s strength, deformation and crushing behaviour.     

Improving the functional properties of fish gelatin by conjugation with the water-soluble fraction of bitter almond gum

Food Science and Biotechnology - Maillard-based conjugation may be a useful way of improving the functional properties of food biopolymers. In this study, covalent attachment of fish gelatin (FG)...     

Effect of deep cryogenic processing on tensile toughness of 45WCrV7 steel

Toughness is an important property for being used in steels in engineering applications. In this research, tensile toughness of 45WCrV7 steel was measured and calculated in 10 different processing conditions. The results of tensile test showed that two samples had maximum tensile toughness. Microstructural studies demonstrated that the required condition for high tensile toughness was simultaneous increase in two microstructural factors named content and population density of the secondary carbides because a matrix which was poor of carbon and alloying elements was softened and thus increased total tensile toughness.     

Controlled Growth of Conductive AlN Thin Films by Plasma-Assisted Reactive Evaporation

Metallurgical and Materials Transactions A - In this work, the growth of conductive AlN thin films by plasma-assisted reactive evaporation at different filament-to-substrate distances was presented...